Vibratory forming of materials

ABSTRACT

An annular vibrator unit for the vibratory forming of materials, particularly the deep-drawing of metals to axisymmetric shapes. The annulus is axially deeper at the outer rim than at the inner, leading to greater amplification of vibrations introduced at the outer rim. The greater axial depth of this rim also facilitates the mounting of greater numbers of vibration transducers in the rim.

United States Patent [1 1 Biddell et al.

VIBRATORY FORMING OF MATERIALS Inventors: David Colin Biddell, Birmingham;

Graham Robert Dawson,- Bewdley; Dennis Hugh Sansome, Sutton Coldfield, all of England National Research Development Corporation, London, England Filed: Mar. 25, 1974 App]. No.: 454,758

Assignee:

Foreign Application Priority Data Mar. 26, 1973 United Kingdom 14519/73 US. Cl. 72/56; 72/60; 72/467;

72/DIG. 20 Int. Cl. B21C 3/04 Field of Search 72/467, 56, 60, DIG. 20

References Cited UNITED STATES PATENTS 8/1965 Jones 72/253 Primary Examiner-Milton S. Mehr Attorney, Agent, or FirmCushman, Darby & Cushman [57] ABSTRACT An annular vibrator unit for the vibratory forming of materials, particularly the deep-drawing of metals to axisymmetric shapes. The annulus is axially deeper at the outer rim than at the inner, leading to greater amplification of vibrations introduced at the outer rim.

The greater axial depth of this rim also facilitates the mounting of greater numbers of vibration transducers in the rim.

7 Claims, 18 Drawing Figures US. Patent 00:. 7,1975 Sheet 1 of 12 3,910,085

1 6 4 2 l 1 I d W 1 .1 SW 1 2 7 -Jr1- 3 PRIOR ART US. Patent Oct. 7,1975 Sheet 3 of 12 3,910,085

US. Patent Oct. 7,1975 Sheet4 of 12 3,910,085

US. Patent Oct. 7,1975 Sheet5 of 12 3 ,910,085

US. Patent Oct. 7,1975 Sheet 6 of 12 US. Patent Oct. 7,1975 Sheet 7 of 12 3,910,085

U.S. Patent Oct. 7,1975 Sheet 8 of 12 3,910,085

US. Patent Oct. 7,1975 Sheet9 of 12 3,910,085

U.S. Patent Oct. 7,1975 Sheet 10 of 12 3,910,085

U.S. Patent Oct. 7,1975 Sheet110f12 3,910,085

w; m TR US. Patent Oct. 7,1975 Sheet 12 of 12 3,910,085

VIBRATORY FORMING OF MATERIALS This invention relates to the use of vibratory techniques to assist the shaping of materials. In particular it relates to the forming of axisymmetric shapes such as cups from metal blanks, by using a punch to force such blanks through or into a die cavity, and to the forming of tube, rod or like shapes by drawing them through a female die.

It has already been proposed to assist such forming processes by vibrating the die faces in a radial direction that it to say, a direction normal to the drawing axis while drawing proceeds. When cans, for example, are drawn as just described, the advantages to be achieved by such vibration include the ability to draw a longer length of can in relation to the diameter than is possible without such radial vibration, the reduction or elimination of chatter, the capability of the process to tolerate poor lubricants and a reduction in loads. The advantages to be achieved when tubes or rods are drawn are described in co-pending US. patent application Ser. No. 358,391, and include positive deformation work performed by the vibrations; this work supplements what is achieved by the normal drawing forces.

The die faces may be vibrated by making the die a part integral or otherwise of a vibratory unit. For instance by attaching the die to a vibrator member, this member being so constructed and activated that resonant vibrations are set up in the die/member assembly; these vibrations causing the die faces to oscillate in a radial direction. Vibrator members so far proposed to achieve such vibrations have been in the general form of circular metal discs of uniform axial depth, having holes at the centre to receive the die and having means at the periphery to receive vibrator devices, for example magnetostrictive transducers. The use of such vibratory members is subject to limitations, in particular those of size and power consumption. It has sometimes been found that the least radius of vibrator disc that is necessary to create a resonant die/unit assembly is too great for a proposed installation. It has been found also that many known vibrator units of the kind described are inefficient in that although the transducers may set up vibrations of considerable amplitude in those parts of the vibrator unit close to where they are attached (e.g. the periphery), the corresponding vibrations induced at the die faces are much smaller.

The present invention includes vibrator units, and die/member assemblies, of generally circular shape when viewed along the forming axis but which exhibit marked superiority in compactness and/or power requirements compared with more simple disc-type units as already described. The invention includes methods of forming materials using such units.

The invention is defined by the claims and will now be described, by way of example, with reference to the accompanying drawings in which:

FIGS. 1 to 8 show various types of vibrator unit diagrammatically in axial section, and

FIGS. 9 to 18 illustrate the performance of such units graphically.

FIG. 1 shows a known vibrator unit assembly comprising a flat disc member 1, with magnetostrictive transducers 2 mounted at angular intervals in its outer periphery 3. A ring die 4 of known type having a central bore 5 of radius r about the forming axis 6 makes a firm fit within a hole defined by the inner periphery 10 of the disc. The disc has a uniform depth d measured in the direction of the axis 6. In particular this depth d applies at the face 7 of die 4. For the purposes of comparison, all the units according to the present invention and as shown in FIGS. 2 to 84 have this same depth at their radially innermost faces. It will also be noticed that while die 4 and disc 1 are shown as distinct but attached units in FIG. 1, in FIGS. 2 to 8 there is no such separation. This is because the unit comprising the die and vibrator must vibrate as one and because FIGS. 2 to 8 are not to scale and only generally indicate some of the shapes of unit that fall within the present invention. The presence of a separate die at the centre of each of the units shown in FIGS. 2 to 8 would not significantly affect the basic shape, provided that radial resonance is maintained.

FIGS. 2 to 8 are not to scale, but show the general shape of what will be referred to, respectively, as ahalf tapered assembly, a tapered assembly, a half exponential assembly, an exponential assembly, a combined assembly, a tapered sectoral assembly and a step assembly. As already indicated, each assembly has the same axial depth d at its radially innermost face as does the plane disc of FIG. 1, and it may be assumed that each assembly is to be vibrated by transducers mounted at angular intervals in the outer periphery, as in FIG. 1 also.

Such an indication is given for the assemblies of FIGS. 1, 3 and 5 to Sin FIG. 9, in which graphs G1, G3 and G5 G8 correspond to the assemblies shown in the Figures of the same numbers. Each graph refers to an assembly where the inner radius r equals 0.5 inch and d equals 1 inch, and where magnetostrictive transducers are mounted in the periphery of the assembly in the manner indicated in FIG. 1, and vibrate at 13 KHz. For each assembly, the minimum periphery diameter is found at which resonance occurs, that is to say the condition in which the entire assembly vibrates in a fundamental radial mode and vibrations of a constant frequency and amplitude, set up at the periphery, give rise to vibrations of the same frequency, in phase but of different amplitude, at the inner face. The y-axis records units of amplitude, and the x-axis the width of the assembly, i.e. the radial distance from the periphery to the drawing axis 6. The extreme x-co-ordinate of each graph line indicates the least assembly width, which may be predicted by known equations, at which resonance takes place. The y-axis is marked in units of amplitude, and it will be seen that for the purposes of comparison each graph relates to a comparable case in which the inner wall 7 of the assembly vibrates radially with an amplitude of 1 unit, e.g., 0.001 inch.

The term amplification factor will henceforth be used to denote the ratio between the amplitude at the inner wall 7 and the amplitude at the periphery.

Study of the graphs will show that the flat ring represented by G1 requires the greatest width (about 4.6 inches) to achieve resonance, and that the periphery of this disc has to be vibrated with much the greatest amplitude (just over 2.0 units) to create the standard unit vibration at the centre. By contrast graph G7 shows that the assembly of FIG. 7, with an angle of taper of 20 and a radius of 2.5 inches to the inner extremity 8 of the sector-forming slots 9, resonates with an outer radius of just over 3 inches, and only has to be excited to an amplitude of about 1.65 units to set up the necessary unit amplitude at the centre. By contrast also graph G8 shows that the stepped ring of FIG. 8, with dimensions s and t equal to 2 inches and 3 inches respectively, resonates at an outer radius of about 3.75 inches but requires an amplitude of only just over 1.4 units at the periphery to set up unit amplitude at the inner wall 7.

FIGS. to 14 relate to the same parameters as FIG. 9, and give more detailed comparisons between the performance (Graph lines B) of a flat disc assembly and the new types of assembly (Graph lines B) represented in FIG. 9 by graphs G3, G5, G6, G7 and G8 re spectively. In FIG. 10 the flat ring is compared with three tapered assemblies with different angles of taper. The greater the taper, the smaller assembly radius required for resonance and the greater the amplification factor. FIG. 11 compares a flat construction with two rings the surface of which are shaped to an exponential law. The upper of the two graph lines marked B represents a ring with a thicker periphery than that represented by the lower of the said two graph lines. The thicker ring shows the greater amplification factor and resonates at the smaller radius. FIG. 12 shows that with the combined assembly of FIG. 6, outer radius and power losses are both minimised as the radius of the parallel-sided part of the assembly (dimension u in FIG. 6) decreases. FIG. 13 shows that with the tapered sectoral assembly of FIG. 7, size tends to minimise as the common radius (dimension v, FIG. 7) falls. FIG. 14 shows that with the stepped assembly of FIG. 8, losses are minimised as dimension s falls. The particularly flat shape of graph W in FIG. 14, indicating the same amplitude of radial vibration over a considerable radial spread of the assembly, should be noted.

Broadly speaking the main advantage of the radial slots 9 of FIG. 7 is that they inhibit the formation of hoop stresses within the assembly and the consequent hoop resonances that tend to cancel the radial resonances which the assembly is meant to generate. The advantages of the particularly high amplification factor of the stepped assembly (FIG. 8), and the advantage of this design and the combined assembly (FIG. 6) in having flat ring-like cenres which can seat easily against adjacent flat surfaces, must be weighed against the high stresses which are created in such assemblies close to the steps, and which make such assemblies liable to fracture by fatigue at these points.

FIG. 15 is to a different scale from the previous figures and compares the performance of the assemblies of graphs G1 and G7 of FIG. 9 over a wider range of assembly radius. Points 10 and 11 correspond to the right-hand extremities of graphs G1 and G7. To achieve resonance within circular assemblies of the type we have been considering, it is well recognised that vibrational stress nodes must exist at the peripheries. In FIG. 15 points 12 and 13 indicate those assembly radii at which the next stress nodes will exist. The crossing by the graphs of the x-axis indicates that the vibrations at the peripheries of these new radii will be in anti-phase to the vibrations at the centre. The radius of the sectoral assembly at point 13 is this time fractionally greater than the radius of the flat disc assembly, but now the amplitude that needs to be imparted to the periphery of the sectoral assembly is little over half that which the plane assembly requires to generate unit amplitude at the centre. The amplitude at the periphery of the sectoral assembly is in fact only about 0.6 unit,

which is of course less than that which is set up at the centre.

FIGS. 16, 17 and 18 are on the scale of FIG. 15 and show the result of increasing to 2 inches the dimension r for assemblies of the type represented by graphs G7, G8 and G6 of FIG. 9. The only useful peripheral radius at which transducers can be mounted to achieve resonance now corresponds with a position of the graph lying below the x-axis, like points 12 and 13 in FIG. 15. This results in vibrator assemblies of large diameter, but has the advantage of requiring only small amplitude oscillations to be set up at the periphery. In particular it may be noted that vibrations of an amplitude of only 0.2 units need be set up at the periphery of the combined (G6-type) assembly of FIG. 18, with an outer radius of nearly 11 /2 inches.

Alternatives are of course possible to the use of magnetostrictive transducers to vibrate the assemblies. These could include individual piezo-ceramic crystal units, particularly but not exclusively suitable to sectoral units of the G7 type; continuous circumferential piezo-ceramic units, which may be particularly suitable for all except the sectored units, and which unlike the magnetostrictive transducers could possibly be mounted in the assemblies at radii inboard of the outer periphery; and transducers of the window-stack magnetostrictive type. The greater axial depth of all the assemblies at their outer, compared with their inner, peripheries naturally facilitates the mounting of more transducers at the outer rim than would be possible if the axial depth there were no greater than at the inner rim. For instance the greater depth allows transducers to be mounted in two rows, as indicated in FIG. 2.

We claim:

1. A vibrator unit for use in the vibratory forming of materials comprising:

a member of generally annular shape disposed around a central axis and having an inner peripheral surface and an outer peripheral surface axially deeper than said inner peripheral surface, and at least parts of said inner peripheral surface lying in the same transverse planes, relative to said central axis, as parts of said outer peripheral surface; and

means to receive vibrators formed in said outer peripheral surface.

2. A vibrator unit according to claim 1 in which substantially all parts of said inner peripheral surface lie in the same transverse planes as parts of said outer peripheral surface.

3. A vibrator unit according to claim 2 in which said outer peripheral surface lies parallel to said central axis.

4. A vibrator unit according to claim 1 in which the depth of said unit, measured in directions parallel to said central axis, increases continuously from said inner peripheral surface to said outer peripheral surface.

5. A vibrator unit according to claim 1 in which the depth of said unit, measured in directions parallel tp said central axis, increases in steps between said inner and said outer peripheral surfaces.

6. A vibrator unit according to claim 1 in which radial slots are formed in said unit from points spaced equally around said outer peripheral surface, said slots stopping short of said inner peripheral surface.

7. A vibrator unit according to claim 1 further including a plurality of vibrators disposed in said receiving means. 

1. A vibrator unit for use in the vibratory forming of materials comprising: a member of generally annular shape disposed around a central axis and having an inner peripheral surface and an outer peripheral surface axially deeper than said inner peripheral surface, and at least parts of said inner peripheral surface lying in the same transverse planes, relative to said central axis, as parts of said outer peripheral surface; and means to receive vibrators formed in said outer peripheral surface.
 2. A vibrator unit according to claim 1 in which substantially all parts of said inner peripheral surface lie in the same transverse planes as parts of said outer peripheral surface.
 3. A vibrator unit according to claim 2 in which said outer peripheral surface lies parallel to said central axis.
 4. A vibrator unit according to claim 1 in which the depth of said unit, measured in directions parallel to said central axis, increases continuously from said inner peripheral surface to said outer peripheral surface.
 5. A vibrator unit according to claim 1 in which the depth of said unit, measured in directions parallel tp said central axis, increases in steps between said inner and said outer peripheral surfaces.
 6. A vibrator unit according to claim 1 in which radial slots are formed in said unit from points spaced equally around said outer peripheral surface, said slots stopping short of said inner peripheral surface.
 7. A vibrator unit according to claim 1 further including a plurality of vibrators disposed in said receiving means. 